Automatic choke



Oct. 25, 1938. G. R. SISSON 2,134,421

AUTOMATIC CHOKE Filed Feb. 17, 1933 Skim-N Patented Oct. 25, 1938 UNITED STATES NT. OFFI f 2,134,421 7 V s AUTOMATIC CHOKE Glen R. Sisson, Pendletonp I I Application February 17,1933, seriairm'ssmn 1 Claim. (01. 123-179) My invention is concerned with automatic control of the proportions of the mixture produced in the carburetor of an internal combustion engine. It is the object of my invention to produce a device which willautomatically control mixture proportions in accordance with temperature, which will provide a temporary enrichment when the engine is being cranked, which will not interfere with satisfactory performance of the engine under either wide open or closed throttle, which can be simply and economically constructed, andwhich may be very easily installed.

In carrying out my'invention, I provide the carburetor-with a choke-valve of the butterfly type which is eccentrically pivoted so as to tend to swing toward open position under the influence of air which passes it, and I provide for this choke- .valve a yielding temperature-responsive loading element which yieldingly opposes opening movement of the choke-valve .under the influence of .the air flowing past it. The controlof the chokevalve effected by the temperature-responsive loading element is supplemented by. two mechanisms one of which is operable when the engine is being cranked to prevent movement .of the choke-valve 'underthe influence of the air. flowing past it and the other of which is controlled jointly with the throttle valve to limit to a predetermined extent the choking efiect produced at open and closed throttle positions. 7

The accompanying drawing illustrates an embodiment of my invention: Fig. 1 is :a somewhat diagrammatic showing of an engine equipped with a mixture-control device embodying my invention; Fig. 2 is a horizontal section through my device on the line 22 of Fig. 3; and Fig. 3 is a front elevation of the device with parts thereof broken away.

Indicated diagrammatically in Fig. l are the inlet and exhaust manifolds l0 and H of an internal combustion engine, a carburetor 12 connected to the inlet manifold I0, an electric enginestarting motor 13, a battery M for supplying electrical energy to the motor l3, and a starter switch 15 through which the motor l3 may be connected to the battery I l. The carburetor I2 is shown as provided with the usual throttle valve 13 and a choke-valve I1 mounted in the air-inlet opening l8 of the carburetor [2.

The choke-valve H, as is clear from Fig. l, is pivoted on an eccentric axis in the carburetorinlet passage I8, whereby the flow of air past it tends to swing it toward open position. For the purpose of controlling the extent of the opening movement of the choke-valve, I provide a temperature-responsive element which is responsive to engine temperature and :which permits the choke-valve to approach wide-openposition as the engine temperature increases; i

As shown inthe drawing, the temperature-re- .2 .sponsive element just referred to comprises .a

spirally coiled bimetallic strip the outer end of which is fixed to a housing .ZPmounted ion'the side of the exhaust manifold H .and the inner end of which is secured to 'a irotatable shaft 2.2

supported from the housing 2|. Mountedon the outer end of the shaft 22 'isan arm 23 connected through a link to the choke-valve H. The

parts ar'eso arranged that as the temperature As shown in" Fig. 2, this e'lectro-magnetic brake comprises a cup-shaped member 30 of magnetic material and a central hub-like member 3| associated-therewith and also made of magnetic material; 'The two members 30 and 3| constitute thepole pieces of an electro-magnet winding 33 which surrounds the member 3| within the flange-of the cup-shaped member '30. The two pole pieces and 3| are outwardly directed, and 7 immediately beyond them on the shaft 22 there is secured a disk 34 of magnetic material which constitutes the armature of the electro-magnet.

A cover 36, the inner end of which fits over the cylindrical housing 2|, encloses the electromagnet and the disk 34 and provides a support for the outer end of the shaft 22. The shaft 22 is not only rotatable inits support but is also axially slidable through a distance sufficient to per--v mit the armature to move into and out of engagement with the pole piece 30. The resiliency of the bimetallic strip 20 serves normally to hold the armature 34 out of engagement with the pole piece 30; but when the electro-magnet 33 is en- 7 ergized, the armature 34 and shaft 22 will be drawn inwardly, causing the bimetallic strip to be drawn to the dotted-line position indicated in Fig. 2. Upon de-energization of the electromagnet 33, the bimetallic strip 20, as the result of its resilienecy, will be returned to its normal plane and will carry the shaft 22 and armature 34 outwardly.

' As is clear from Fig. 1, the electro-magnet 33 is connected in parallel with the starter motor I3 so as to be energized whenever the starter motor is operative. Therefore, when the startermotor switch I5 is closed, the magnet 33 is energized and draws the armature 34 inwardly into contact with the pole-piece 30 thus braking the shaft 22 and preventing air flowing past the choke valve I! from moving it toward open position beyond that position in which it was held by the temperature-responsive element 20 before the starter switch l5 was closed. When the engine begins to operate under its own power and the starter motor switch 5 is opened, the magnet 33 is de-energized, thus permitting thearmature 34 and shaft 22 to move outwardly. This relieves the braking effect and permits the choke-valve I! to swing toward open .position under the load imposed by the temperature responsive element 20. This movement of the choke-valveproduces a decreased enrichment of the mixture; and as the engine-temperature increases; the temperature-responsive element 20 continues to move the choke-valve toward open position until when normal operating temperature of the engine is attained the choke-valve will be completely open.

I have found that it is desirable to impose upon the choke-valve control afi'orded by the temperature-responsive element 20 and the elec- :tro-magnet 33 a further control in accordance with throttle-position. This additional control limits the choking effect at both closed-throttle and open-throttle positions. The former I find especially desirable to prevent too great a choking effect as the result of the low-air-velo'citypast the choke-valve when the throttle is closed, and

.thelatter is advisable to prevent the choke-valve from unduly restricting air-flow through the carburetor at wide-open throttle. a

To veffect control of the choke-valve in accordance with throttle-position, I provide on the disk 34 two outwardly projecting abutments and 4| which co-operate respectively with inwardly extending pins 42 and 43 secured on opposite sides of the pivotalaxis of an arm 44 pivotally mounted on the outside of the cover 36 and con% nected to'the throttle-valve |6 by means of a link 45. Choking movement of the shaft 22 is limited by the co-operation. of the two pairs of abutments 40-42 and 4|43. 7

Figs. 1 and 2, and Fig. 3 in full lines, indicate the condition of the device at intermediate throttle position and with the engine cool. The parts are so arranged that as the throttle is closed the arm 44 is swung upwardly to lower the pin 42 toward its association abutment 40 on the armature 34. Further, the relative locations of the abutments 40 and 4| and the pins 42 and 43 are such that when the throttle is near the mid-point ofits range of adjustment thepins 42 and 43 do not interfere with complete closing of the chokevalve. Upon extreme closing movement of the throttle, however, the arm 44 is swung upwardly to a point near the upper dotted-line position shown in Fig. 3, thus lowering the pin 42 to such an extent that it will be engaged by its associated abutment 40 to limit closing movement of the choke-valve short of completely closed position. Similarly, when the throttle is moved to its extreme open position, the arm 44 is lowered to the lower dotted-line position illustrated in Fig.3, and the .pin 43 swings downwardly with it to co-operate with the abutment 4| in preventing'the choke-valve from being completely closed. I

By reason of the construction just described, it will be apparent that if the engine is running either under completely closed or completely open throttle the choke-valve can not be completely closed. 1

In order to prevent the abutment 40 and pin 42 from preventing complete closing movement of the choke-valve during cold starting should the throttle be closed; the pin 42 is made short enough so that'the abutment 40 will pass out of engagement with it as the armature 34 and shaft 22 are drawn inwardly when the electro-magnet 33 is energized. The pin 43, on the other hand, is long enough to remain in engagement with its associated abutment 4| on the disk 34 under all conditions, and thus it is always possible, by moving thethrottle to wide-open position, to open the choke-valve and correct any tendency of the device to cause flooding of the carburetor.

I claim as my invention:

In combination with an internal combustion engine having a carburetor provided with an unbalanced choke-valve, a rotatablefshaft connected to said choke-valve to operate it, a temperatureresponsive element for rotating said shaft, a brake associated with said shaft, and mechanism operative during cranking of the engine for actu ating said brake.

, GLEN R. SISSON. 

